GROWTH-MECHANISM OF LAYER CONTROLLED BI2SR2CAN-1CUNO2N+4 FORMED BY LASER MOLECULAR-BEAM EPITAXY

For the investigation of the first step of the thin-film formation of Bi2Sr2Can-1CunO2n+4, the surface of SrTiO3(100) substrate and the growth of a SrCuO2 thin layer on that substrate have been studied. It is confirmed that the topmost layer of the native SrTiO3(100) substrate is a TiO2 layer. This surface layer is changed to SrO by the supply of Sr atoms in a NO2 atmosphere. When Sr and Cu are supplied simultaneously on the substrate surfaces to form SrCuO2, either a SrO or a CuO2 layer is the surface layer dependent upon the composition of the substrate surface. By the successive supply of the sub-unit cell layers of Bi2Sr2Can-1CunO2n+4 the structures are formed. The RHEED pattern shows streaks all through the growth, indicating the two-dimensional layer growth in all the steps controlled within monolayer accuracy.